1. Field of the Invention
This invention relates to rear screen projection systems.
2. Description of Related Art
The first commercially available "big screen TV's" typically had a large screen and a projector that displayed a picture onto the screen. The projector typically reflected the picture off of the screen and into the audience. When used in an airplane, sunlight would come through the windows and also reflect off of the screen. This external light would tend to "wash out" the picture being displayed. The quality could only be improved by having the passengers pull down the window shades, a somewhat impractical method to use on a commercial airplane.
Another problem typically associated with large screen projection systems is that the top, center and bottom portions of the picture have different focusing requirements. This problem occurs because the projector is usually placed above the screen, wherein the distance between the projector and the bottom of the screen is longer than the distance between the projector and the top of the screen. Currently the picture is focused with a complex lens, which requires an undesirable length of time to focus the picture and install the system. One obvious solution is to place the projector in the center of the screen, such that the distance between the projector and the edges of the screen are the same. This is not practical because the projector would then be in the way of those behind the projector. Additionally, when installed on an airplane the projector could create an overhead protrusion which could be a safety hazard on the plane.
It has also been found that the picture quality improves when the incidence of light is perpendicular to the screen. With an overhead projection system the screen would have to be tilted toward the projector, creating a system that would direct the picture toward the ceiling instead of down into the audience. To create a system with a screen pointing downward, the projector would have to be on the floor. A floor mounted projector would take up valuable seating space and would be highly undesirable when used on an aircraft. Thus what is needed is a compact large screen projection system utilizing an overhead projector and a screen that displays a bright clear picture, that can be installed into the passenger cabin of an airplane.